MEXICO CITY, Mexico (CNN) -- Hundreds of thousands of bus and truck drivers are threatening to go on a prolonged strike if the federal government does not do something about rising motor fuel costs.

About 500,000 commercial and public vehicle drivers took part in a one-day strike Monday that affected 16 of Mexico's 31 states and the federal district, reports said. Many of the drivers parked their vehicles on highways, snarling traffic and frustrating motorists.

The strikers want the price of diesel to drop about 24 percent, from 7.63 pesos (about U.S. 54 cents) per liter to 5.96 pesos (about 41 cents).

About 50 million Mexicans -- most of them bus riders -- were affected, said Edmundo Delgado Ramirez, head of the National Confederation of Commercial Transporters of the Mexican Republic.

Problems were reported in all parts of the nation.

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In the state of Mexico, at least 100 drivers paralyzed northbound lanes of the Mexico-Queretaro freeway, El Sol de Mexico newspaper reported. The strikers met in front of a Ford Motor Co. assembly plant at 8 a.m. and then drove a caravan on the freeway until 2 p.m. at 10 kilometers per hour (6 miles per hour), the newspaper said. The strikers carried banners demanding lower diesel and gasoline prices.

In Coahuila, on the U.S. border, at least 2,500 vehicles participated in the strike, affecting 500,000 people, El Universal newspaper said.

In the state of Aguascalientes, bus service operated at 60 percent, with 278 of 695 buses not in service, El Universal said. About 70,000 riders were affected, the newspaper said.

In Chihuahua, also on the U.S. border, about 100 truckers and bus drivers blocked one lane of the Chihuahua-Delicias freeway.

In Chiapas, 3,000 of the 24,000 passenger and cargo vehicles participated in the strike, said Bersain Miranda, the president of a transportation union.